1. Technical Field
The present invention relates to a method for fabricating a substrate for transfer printing and a substrate for transfer printing fabricated thereby. More particularly, the present invention relates to a method for fabricating a substrate for transfer printing using a handling substrate having a concave-convex structure, a substrate for transfer printing fabricated thereby, and application thereof.
2. Description of the Related Art
As future electric/electronic devices are required to be mounted not only on simple planar surfaces, but also on various surfaces, such as skin surfaces, clothes surfaces, interior or exterior surfaces of buildings, body surfaces of persons, and the like, the devices need to have highly mechanical flexibility. Since flexibility of the devices can be easily obtained through a smaller thickness thereof, substrates used for the devices are required to have as small a thickness as possible. However, when the thickness of the substrate decreases to several micrometers or less, the substrate inevitably undergoes twisting or other deformation due to mechanical flexibility of the substrate in the course of processing. Thus, a handling substrate is used to support an ultrathin substrate in order to secure process stability. In this case, however, a process of transferring a thin film type device formed on the ultrathin substrate through separation from the handling substrate to transfer the device to another surface is required. At this time, alignment and transfer yield are very important. In this regard, it is important to take three factors into account: first, the ultrathin substrate must retain mechanical stability in the manufacturing process; secondly, an initial arrangement pattern of the ultrathin substrate must be maintained in the manufacture and transfer printing processes of the device; and thirdly, transfer printing must be performed at high yield.
In one example of transfer printing, an ultrathin substrate is directly coated on the handling substrate. Although this method can provide process stability, there can be difficulty in transfer of the ultrathin substrate to another substrate due to high adhesion force between the handling substrate and the ultrathin substrate. Accordingly, it can be contemplated that a device is fabricated on the ultrathin substrate, with a sacrificial layer interposed between the handling substrate and the ultrathin substrate, and is then transferred after removing the sacrificial layer from the handling substrate. However, when removing the sacrificial layer using an etching solution, the pattern of the ultrathin substrate placed on the handling substrate floats causing loss of initial arrangement, and sinks into the handling substrate causing deterioration of transfer yield. Meanwhile, in another method, an insulation layer can be interposed between the handling substrate and the ultrathin substrate to allow the device to be separated from the handling substrate upon laser irradiation, causing increase in manufacturing cost and a possibility of damaging the device by a laser beam. Moreover, this method suffers from performance deterioration of the device due to formation of an uneven surface upon detachment from the handling substrate.
Therefore, there is a need for a method of manufacturing a device on an ultrathin substrate, which can maximize the degree of alignment and transfer yield of the device in the course of transfer printing, while securing process stability.